Preliminary studies on the bacterial and parasitic microflora and microfauna of domestic sewage in northern Jordan

Abstract

Domestic sewage of the city of Irbid in northern Jordan is mainly treated by an activated sludge process and for one stage only. Various types of heterotrophic Gram negative bacteria were isolated from sewage samples at all stages of treatment. Raw sewage was found to contain Proteus vulgaris, Escherichia coli, Klebsiella pneumoniae, Enterobacter aerogenes, Aeromonas hydrophilia and Pseudomonas aeruginosa. The percentage removal of bacteria attained by settling tank effluent (El) was 95%. However, 14 colonies per ml of E. coli and P. vulgaris were counted in treated final effluent (E2). About 23% of the bacterial population of sewage sludge was 5. typhi. Shigella sonnei was the only Shigella species found in digested sludge. Chlorella, Chlamydomonas and filamentous cyanobacteria were also found in the aerated and finally treated effluent samples. Non‐pathogenic bacteria were found only in effluent, i.e. E. coli and P. vulgaris. The percentage removal of parasite cysts and ova from finally treated effluent was 67% from Entamoeba coli, 100% from Giardia spp., 88% for Ascaris lumbericoides and 100% for Parascaris equorum. Parasitic species potentially infective to man were detected in sewage samples. The number of parasite and/or parasite ova varied for the different species and their numbers also varied at different points of the sewage treatment works. Digested sludge and sludge had the highest number of parasites. Three parasite species, Entamoeba coli, Entamoeba histolytica and Ascaris lumbericoides were detected in final effluent at concentrations of 20,50 and 10 per litre respectively.

Keywords:

• sewage
• bacteria
• parasites
• Jordan